Basically, all codecs you have installed can be uninstalled. SOme from Control Panel's Add\remove, some from start->programs. But I tend to believe you have installed codecpacks and not individual codecs.
Codecpacks usually come with a lot of codecs, most of them not needed, and sometimes with conflicts. They are well intended but sometimes is better not to use them.
Try to read here:
http://forum.bsplayer.org/viewtopic.php?t=3042